Most of the leasehold properties I see in my job are flats and all tend to be for about 125 years if granted this side of 2000.
If it's a new build you're pretty much guaranteed to obtain that sort of term, but as somebody else has pointed out its a bit rarer to see it on a house and for that purpose I would want to avoid a Leasehold house as well especially if you're considering it as a potential "family home" as you may want to extend the property, convert the loft etc all which will usually require a licence to alter from the Landlord as well and they may be able to, terms of the lease permitting, refuse you anyway.
Also remember that with ground rents, services charges (more common for blocks of flats) and insurance costs, if you fail to pay those and fall into arrears you're likely to have solicitors sending you letters and in extreme cases they can and will forfeit your lease and evict you. Items such as these are often subject to review at certain periods as well, for instance one lease I was looking at today had a basic ground rent of £200 (I cant remember if it was per quarter or half yearly, if it was London it was more likely to be per quarter) which then after the first 25 years doubled to £500. Services charges also subject to review at certain periods as in line with the lease and depending on what the Landlord deems necessary for repairs etc they will try to form what they deem to be a reasonable amount to cover those works. There's a lot of protection for tenants/leaseholders in that sort of situation though with the LVT publishing a fair few of its decisions on such matters. Overall It's an area full of financial hazards in my opinion and experience.
With flats, when all the leaseholders purchase the freehold it's known as collective enfranchisement.